This invention relates generally to phase mirror arrays, and more particularly the invention relates to a microactuator for a phase mirror array.
In optical displays, switches, and maskless lithography systems, patterns can be created by modulating individual mirrors in a micromirror array to produce selected bright and dark spots (“pixels”) in an image. In the conventional approach, as exemplified by the Texas Instrument commercial mirror arrays, the mirror is mounted on a cantilever (FIG. 1). Selected mirrors can be tilted such that incident light from those mirrors is out of the pupil of the imaging objective. Variations on this system have been proposed including producing a “gray scale” (partial illumination of certain pixels) in the image plane. In another approach, individual mirrors, also called phase mirrors, are shifted in the plane of the mirror to produce an image by interference effects (FIG. 2).
In some applications, the phase-mirror approach produces more useful images. However, no practical approach has been proposed to construct an electrostatically actuated dense array of flat phase micromirrors of micrometer size. For example our colleagues at Stanford University are concentrating on the use of elastomers to support the mirrors (FIG. 3). Numerous problems need to be overcome to make this approach practical, including making electrical connection to the top mirror without sacrificing mirror space, finding a suitable elastomer, fabricating the device by semiconductor-compatible process steps, designing a mirror with low voltage actuation, and so forth.